1. Field of the Invention
The present invention relates to the oral delivery of glycosidic and related antibiotics which by this route are poorly absorbed and more especially to the enhancement of this delivery by formulations which contain a hydroxyaromatic acid.
As employed in this application, the term "glycosidic and related antibiotics" refers to those antibiotics which contain a carbohydrate moiety which is attached through a glycosidic bond and includes such antibiotics as the macrolides, aminoglycosides, lincomycins and anthracyclines.
2. Description of the Prior Art
It is well known to the art that a number of antibiotic agents are only slowly absorbed from the gastrointestinal tract. Consequently, said antibiotic must be administered by the intravenous or intramuscular route or in excessively large oral doses in order to attain clinical efficacy. The .beta.-lactam antibiotics is one class of antibiotic which is poorly absorbed by the oral route. Similarly, the glycosidic and related antibiotics, which are chemically characterized by a chemical structure which includes a carbohydrate moiety bonded to the remainder of the molecule by a glycosidic linkage, are poorly absorbed by the oral route. The glycosidic and related antibiotics, such as the macrolide, aminoglycoside, lincomycin, anthracycline and other chemically related antibiotics, are poorly absorbed from the gastrointestinal tract because of two properties, hydrophilicity and/or acid instability. The hydrophilic, polar nature of these antibiotics precludes their rapid absorption so that even the small percentage which is absorbed is subject to a long residency time in the gastrointestinal environment. It is therefore clear that any factor which enhances the rate of absorption will demonstrate improved clinical efficacy.
Many attempts have been made to improve the oral absorption of glycosidic and related antibiotics. Acid instability is partially overcome by coating the antibiotic with an acid stable-base labile enteric coating. This procedure has achieved some success with the acid labile, macrolide antibiotic, erythromycin; however, this procedure still does not allow complete absorption. Other approaches center on the reduction of the hydrophilicity of the glycosidic and related antibiotics by preparing chemical derivatives which are more lipophilic, see Murphy, Antibiotic Annual 1953-1954, page 500; Stephens, Antibiotic Annual 1958-1959, page 346; and Jones, Journal of Medicinal Chemistry, Volume 15, page 631, 1972. These lipophilic esters of erythromycin show enhanced blood levels when administered to warm-blooded animals.
The many attempts to enhance the oral absorption rate of glycosidic and related antibiotics have met with limited success with the macrolide antibiotics such as erythromycin and oleandomycin and with the lincomycin antibiotics. In these cases specialty coatings and lipophilic chemical derivatives have demonstrated improved absorption from the gastrointestinal tract, but in most cases absorption is incomplete. When similar techniques were applied to the aminoglycoside and anthracycline antibiotics, little or no oral absorption was reported. There is no oral dosage form for either of these two important classes of antibiotics.
Thus, there exists a clear and present need for a novel method to enhance the oral absorption rate of glycosidic and related antibiotics, particularly the macrolide antibiotics.